OSLO, April 24 (Reuters) - Hexagon Chief Executive Ola Rollen was back in court on Wednesday as Norwegian prosecutors sought to reverse his earlier acquittal over alleged insider share trading.

One of Sweden's best known business leaders, Rollen has always denied any wrongdoing and continued to run Hexagon, which he has led since 2000, transforming it from a lowly-valued conglomerate into a $20 billion technology market leader.

Rollen, who was cleared of all accusations in an unanimous verdict last year, risks a prison sentence if found guilty over his 2015 purchase of shares in Next Biometrics, a Norwegian firm unconnected to Hexagon.

"What is the key in this case? Rollen bought shares at the same time that he had insider information," lead prosecutor Marianne Bender told the Borgarting appeals court. "He cheated. He knew something that other investors did not know."

Asked by judge Eirik Vikanes if he admitted any guilt, Rollen replied "No".

The appeal is scheduled to last until May 29. (Reporting by Gwladys Fouche, writing by Terje Solsvik, editing by Alexander Smith)